A natural gas pipeline ruptured in a marshy area of Terrebonne Parish on Monday, sending flames more than 100 feet into the sky and burning for nine hours, the pipeline owner and Louisiana officials said Wednesday. The fire occurred on the Texas Gas Pipeline in Ship Shoal Block 20 in Mudhole Bay near Lake Mechant. No one was hurt in the blaze.

Liz Johnson, a spokeswoman for Texas Gas Transmission LLC, the Kentucky company that owns the pipeline, which delivers natural gas from offshore platforms to Indiana, said the incident happened about 12:15 p.m. Monday. The company shut off a valve to isolate the line, and the gas in the line burned itself out about 9:30 p.m. "We don't know the cause. We're investigating," Johnson said.

Rodney Mallett, a spokesman for the Louisiana Department of Environmental Quality, the lead agency in charge of the incident, said that Texas Gas is required to send the state a letter in seven days with its findings. Texas Gas has hired the Belle Chasse company Oil Mop LLC, which now does business as OMI Environmental Solutions, to clean up any residual oil.

Mallett said the fire was large. "The flames were pretty impressive. From what I hear, they were about 100 feet high," he said.

Ben Walker, assistant director of the Terrebonne Parish Office of Emergency Preparedness, said the fire helped prevent the natural gas from forming a release cloud. Walker said the fire was only in the immediate area, but some reports said the fire was 800 feet high.

If that were true, it would mean the fire was about 100 feet taller than One Shell Square, the tallest building in Louisiana.

The incident was discovered by SkyTruth, a nonprofit that monitors satellite imagery and filings to the National Response Center, the federal clearinghouse for hazardous material incident reports.

John Amos, president of SkyTruth, said that ever since the BP well blowout, a consortium of groups stepped up their monitoring of pollution in the Gulf of Mexico area. There are pollution releases almost daily in areas that are difficult to see or reach, Amos said, and there is little investigation beyond what information the polluters provide. "There's a lot of incentives for them to underplay the severity of incidents," he said.

For the Texas Gas Pipeline fire to show up on satellite imagery, it had to be at least 1,300 degrees, or hot enough to soften steel, Amos said.

"It's fantastically lucky that this happened out in the marsh were nobody lives rather than in a populated area," Amos said.

Texas Gas Transmission is a subsidiary of Boardwalk Pipeline Partners, a company traded on the New York Stock Exchange whose general partner is Boardwalk GP, LP. That company is wholly owned by the Loews Corp., one of the largest diversified financial companies in the United States and the operator of the Loews hotel in New Orleans.